A promising high-energy-density material Zhang, Wenquan; Zhang, Jiaheng; Deng, Mucong ...
Nature communications,
08/2017, Letnik:
8, Številka:
1
Journal Article
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High-energy density materials represent a significant class of advanced materials and have been the focus of energetic materials community. The main challenge in this field is to design and ...synthesize energetic compounds with a highest possible density and a maximum possible chemical stability. Here we show an energetic compound, 2,2'-bi(1,3,4-oxadiazole)-5,5'-dinitramide, is synthesized through a two-step reaction from commercially available reagents. It exhibits a surprisingly high density (1.99 g cm
at 298 K), poor solubility in water and most organic solvents, decent thermal stability, a positive heat of formation and excellent detonation properties. The solid-state structural features of the synthesized compound are also investigated via X-ray diffraction and several theoretical techniques. The energetic and sensitivity properties of the explosive compound are similar to those of 2, 4, 6, 8, 10, 12-(hexanitrohexaaza)cyclododecane (CL-20), and the developed compound shows a great promise for potential applications as a high-energy density material.High energy density materials are of interest, but density is the limiting factor for many organic compounds. Here the authors show the formation of a high density energetic compound from a two-step reaction between commercially available compounds that exhibit good heat thermal stability and detonation properties.
Over the past century, the search for lead-free, environmentally friendly initiating substances has been a highly challenging task in the field of energetic materials. Here, an organic primary ...explosive featuring a fused-ring structure, 6-nitro-7-azido-pyrazol3,4-d1,2,3triazine-2-oxide, was designed and synthesized through a facile two-step reaction from commercially available reagents. This organic initiating substance meets nearly all of the stringent criteria of environmentally friendly primary explosives for commercial applications: it is free of toxic metals and perchlorate, has a high density, high priming ability, unusual sensitivities towards non-explosive stimuli, excellent environmental resistance, decent thermal stability, high detonation performance, satisfactory flowability and pressure durability, and is low-cost and easy to scale-up. These combined properties and performance measures surpass the current and widely used organic primary explosive, DDNP. The fused-ring organic primary explosive reported herein may find real-world application as an initiating explosive device in the near future.
Abstract
We have investigated the activation characteristics of mining faults and the effect of grouting reinforcement under thick loose layer and thin bedrock of the working face and evaluate their ...impact on the safety of mining at similar working faces. Implementing the geological conditions of the 331 working face of the Yangcun Coal Mine (China) of the Yankuang Energy Group Corporation, we have analyzed mechanically the process of fault activation at first. Subsequently, we have obtained the mechanical criterion of fault slip and the expression of relative strength of the nearby rock mass. Using numerical software we have simulated and analyzed the damage characteristics of different bedrock thicknesses on overlying rocks and faults in the fluid–solid coupling mode. In addition, we have studied the controlling effect of grouting reinforcement on fault activation, which has been verified in the field. The main results of our study show that: 1. The mechanical properties of the rock mass near the fault interface have changed and they are related to the cohesive force of the interface; 2. The water inrush mode of the working face changes under different bedrock thickness, and the thinner the bedrock, the less easily the fault is destroyed 3. The slip of the high-level fault is reduced after the grouting of the fault, the propagation of the fracture zone at the fault is suppressed, the seepage of the aquifer water is prevented, and the safe recovery is realized. The results of our study provide a scientific basis for the secure mining across the fault of the 331 working face of Yangcun Coal Mine. Based on the results of our study the working face can be mined safely from now on and in the future.
Water inrush originating from hidden faults in the coal seam floor is challenging to prevent due to their concealed nature. This paper develops a coupled stress–seepage–damage model for simulating ...rock fracture, implemented using the finite element method. The model is validated against compression-seepage tests on rock samples, capturing realistic dynamics of shear and tensile damage as well as permeability. The model is applied to the 27305 working face of a coal mine in Shandong Province, China, revealing the evolution of water inrush caused by a hidden fault. The results indicate that as the working face progresses, both the floor damage and the internal damage within the hidden fault escalate gradually. When mining reaches 80 m, the hidden fault has been activated internally, and the depth of floor damage reaches 13 m, which still has a certain distance from the hidden fault. At 100 m, the depth of the floor damage has stabilized, while the stress concentration at the hidden fault's tip increases, and it begins to expand if conditions for tensile damage are met. By the time mining reaches 110 m, the hidden fault has expanded 9.2 m in length and connected with the floor damage zone, forming a water inrush channel that links the aquifer to the working face, presenting a significant water inrush risk. This work provides an intuitive approach to understanding the evolution of water inrush from a hidden fault, aiding in the prevention of water inrush disasters in practical engineering applications.
Highlights
A coupled stress-seepage-damage model was proposed to simulate the dynamics of hidden faults during the mining process. The model has been validated with several small-scale laboratory compression-seepage tests to demonstrate its capabilities.
By applying the proposed coupling model to a real-world coal mining operation, we demonstrate the process of hidden faults fracture propagation in the floor strata during the working face excavation, which might lead to a water inrush disaster.
The most critical scenario occurs when concealed faults are positioned beneath the working face, resulting in a significant increase in the compressive stress borne by these hidden faults. This increase continues until a damaged state is reached, thereby triggering the propagation of fractures.
Microseismic monitoring technology proves to be an effective measure to prevent water inrush caused by hidden faults, and in our application, microseismic event distributions near the working face are consistent with our numerical analysis results.
In this paper, a grouting material with low cost and high density was proposed for the reinforcement of large-scale floor cracks. The component screening test, mechanical property test, rheological ...properties test, and impermeability test were conducted to obtain the strength, rheological properties, and permeability of the new grouting materials. In order to fully understand the physicochemical properties of the new grouting material, a total of 12 sets of test pieces were produced using cement, clay, and fly ash as the main body, and foaming agent as the auxiliary material. Each set of the test pieces had different proportions of ingredients, pores conditions, and auxiliary chemical materials (water reducing agents, defoamers). The test results showed that: (1) The optimal proportion of ingredients for the new grouting material (including 1% foaming agent) was: 40% of cement, 30% of clay, and 30% of fly ash. (2) The optimal amount of fly ash for the new grouting material was 30% and the optimal foaming amount for the new grouting material was 1%. The impermeability of the grouting material was 0.7MPa, which reached Level P6. The new grouting material was suitable for the HB rheology model. (3) The pores were uniformly distributed inside the solidified body of the new grouting material. In the later stage, the strength of the solidified body was stable, and the flow loss was reduced. At present, the corresponding proportion of ingredients and the performance parameters of the new grouting material were tested in the laboratory. In the future, it is necessary to further determine the effect of the grouting material in the reinforcement of the floor crack of the coal seam and to improve the proportion of ingredients for the grouting material in the mine sites.
Confined water inrush caused by fault activation is the main form of water disaster in deep mining. With theoretical analysis and similar simulation tests, the mechanism and evolution law of delayed ...water inrush caused by fault activation are revealed. At the theoretical level, the expansion and extension of the internal microstructure in the fault zone under the action of the mining stress field and seepage field are the essential causes of fault activation. Overlying strata movement and surrounding rock creep failure are the basic reasons for delayed water inrush caused by fault activation, and delayed time caused by surrounding rock creep failure is much longer than that of overlying strata movement. A similar simulation test was carried out with self-development solid–liquid coupling with similar simulation materials; the results show that delayed water inrush caused by fault activation with mining includes three stages. Micro-activation stage: Water inrush weakness point is formed because of the expansion and extension of the micro-fissure and structure at the bottom of the fault zone. Macro-activation stage: With the change in the stress of the waterproof coal pillar and surrounding rock, the micro-fissures and structures in the stress relief area and tension area of the fault zone expand and extend sharply; meanwhile, water intrudes into the interlayer stratification of the floor in the stress relief area, forming a strong laminar flow phenomenon, and cracks in the floor form and expand; finally, water-conducting channels in the fault zone and floor are formed. Water inrush stage: The waterproof coal pillar and water-resisting layer fail and are destroyed, and the first confined water inrush point is located at the junction of the waterproof coal pillar and gob floor.
With the continuous increase of the upper limit of coal mining, in mining areas near unconsolidated layers, water and sand inrush disasters occur from time to time, seriously threatening the safety ...of mine production. In this paper, the process of water and sand inrush accidents induced by mining near unconsolidated layers is analyzed using mechanical analysis and numerical simulation methods, based on the principle of silo unloading and arching and combined with actual water and sand inrush characteristics; the critical water and sand inrush arching mechanism is explained. The paper also proposed and established three critical arching mechanics models (interlocking arch, bonded arch, and transition arch), deduced the mathematical expression of interlocking arch and transition arch, and obtained the critical instability conditions of the arch and its influencing factors. The research results have guiding significance for the occurrence of water and sand inrush disasters and the judgment of the degree of damage in mining near unconsolidated layers.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
In this study, we present new two- and three-dimensional resistivity models of the Huya fault region in the east margin of the Tibetan Plateau, imaged with magnetotelluric (MT) method. According to ...those models, a high-angle low-resistivity anomaly beneath the Huya fault is revealed, which is interpreted as a crustal thrust fault. The Minshan Uplift is imaged as a two-layered resistivity structure. The Bikou Block exhibits relatively uniform high-resistivity characteristics in our models, with its basement connected to a high-resistivity body beneath the Longmenshan fault belt. Thus, we infer that the Bikou Block belongs to the Yangtze Block. The Longmenshan fault belt exhibits strips of alternating high- and low-resistivity anomalies in the upper crust, with its middle and lower crust being highly resistive. The middle and lower crust of the western study region shows low resistivity, with its geometry changed greatly as it extends southeastward and upward. This is interpreted as an eastward channel of escaping material of the Tibetan Plateau. However, this channel is imaged to be blocked horizontally by the Bikou Block near the Huya fault, causing part of mid-to-lower crustal material to be upwelling, resulting in the Minshan Uplift. Another part of the low resistivity anomaly extended southeastward and was blocked by the lithospheric high-resistivity body beneath the Longmenshan fault belt, and then extended to the northeast and the southwest.
•We obtained the 3-D resistivity model of the triangular area of the northeastern margin of the Tibetan Plateau firstly.•A low-resistivity layer in the middle and lower crust extended southeastward was mapped, and was interpreted as crustal flow.•The earthquakes in this region were controlled by the upwelling of the low-resistivity layer.
The coal mine accidents seriously affect the safety and efficiency of mining for coal mining enterprises. The reliable emergency rescue (ER) processes are explored to minimize the loss of accidents. ...This paper introduces the stochastic Petri net (SPN) and Markov chain (MC) models based on the system structure flow to analyze the ER processes of coal mine accidents. In addition, a triangle fuzzy strategy is presented to optimize the SPN model. The “9·28” major water inrush accident in Shanxi Fenxi Zhengsheng Coal Company of China is adopted to evaluate the time performance and accident data of the ER process. The MC model-based steady-state probabilities of the system under various states are used to calculate the average delay time of this system. The triangular fuzzy strategy is used to analyze the change value of the total time in the ER system at the unit transition speed when the firing rate of each transition is changed, which finds the most time-consuming key activities in the ER process. The results show that SPN and MC can reflect the dynamic behaviors of ER process, which provides a reference for the rescue operations of other coal mine accidents. The triangular fuzzy strategy can quickly find out the key activities affecting the ER time, which greatly decreases the calculations generated by analyzing the total time of the system changed at the unit transition speed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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